1. Field of the Invention
This invention relates to a ceramic rotor which is suitable for a supercharger, a turbocharger, or a gas turbine engine.
2. Description of the Prior Art
From the standpoint of saving energy, improvement in the efficiency of an engine has been recently studied. For example, by supercharging air into engines or by raising the engine operating temperature experimenters have hoped to increase the efficiency of engines. Rotors for such engines are exposed to a high temperature gas and required to revolve at a high speeds, and in the case of superchargers, turbochargers, and gas turbine engines, the rotor rotates at a peripheral speed of 100 m/sec or higher in an atmosphere of 800.degree. C. to 1,500.degree. C. Thus, a very large tensile stress is applied to the rotor, so that the rotor must be made of material having an excellent high-temperature strength. Materials for such as, nickel-cobalt-base heat-resisting metals have been used for rotor construction, because the conventional heat resisting metals have difficulty in withstanding temperatures in excess of 1,000.degree. C. for long periods of time. Additionally, the conventional heat-resisting metals are costly. As a substitute for the heat-resisting metals, the use of ceramic materials with excellent high-temperature characteristics such as silicon nitride (Si.sub.3 N.sub.4), silicon carbide (SiC) or sialon have been studied.
The ceramic rotors of the prior art made of the above-mentioned ceramic materials have a serious shortcoming in that, when a large tensile stress is applied to the ceramic portion of the rotor during high-speed rotation at a high temperature, the ceramic portions are susceptible to catastrophic failure caused by the high tensile stress applied thereto because the ceramic material is brittle. Thus, a very strong ceramic material with an extremely high modulus of rupture is required to withstand the large tensile stresses.